Hydraulically operated control system



Nov. 13, 1962 J. H. BE VlER ETAL 3,053,425

HYDRAULICALLY OPERATED CONTROL SYSTEM Filed April 27, 1959 4 Sheets-Sheet 1 INVENTORS JbJEPH H1 BE V/ER BY WILL/AM 5.55 V/ER ATTOFNE Vs Nov. 13, 1962 J. H. BE VIER ETAL Y 3,063,425

HYDRAULICALLY OPERATED CONTROL SYSTEM Filed April 27, 1959 4 Sheets-Sheet 2 FIGQB INVENTORS J OSEPHMBE VIE BY LLIAME.5&MER

w Y L 1"" V lv-ramsvs Nov. 13, 1962 J. H. BE VIER ETAL 3,063,425

HYDRAULICALLY OPERATED CONTROL SYSTEM 4 Sheets-Sheet 3 Filed April 27, 1959 FIG. 5

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Nov'. 13, 1962 HYDRAULICALLY OPERATED CONTROL SYSTEM 4 Sheets-Sheet 4 Filed April 27, 1959 ggA INVENTORS .bsL-"PH/iBEV/ER United States Patent 3,063,425 HYDRAULICALLY OFERATED CGNTRGL SYSTEM Joseph H. Be Vier, 5638 Chou/en Ave. S., Minneapolis,

Minn., and William E. Be Vier, 4544 York Ave, Minneapolis 10, Minn.

Filed Apr. 27, 1959, er. No. 899,246 7 Claims. (Cl. 121-451) This invention relates to new and useful control systems for hydraulic appliances and particularly relates to new and useful improvements in systems for providing remote control of one hydraulic appliance or apparatus by another hydraulic appliance or apparatus.

Many attempts have been made to provide hydraulic control circuits for remote control apparatus but these have suffered from defects in that they either have had no separate control circuits and relay on the operator to pro vide all control (thus making the circuit incapable of fine adjustment and more or less effective, depending upon the operators skill), have a control connected by a mechanical linkage which is susceptible of only a few situations, or have no sensing ability or provision for correcting misadjustment between remote and control apparatus.

The subject invention consists of two circuits, control and power, which are distinct but communicating. It maintains a follow-up function, a position sensing function and a power application function by complete hydraulic means. A master (or originating) element of the control system is at the power end of the system which is the opposite of conventional arrangements. Positioning adjustment of control elements is provided in the slave (or following) element of the control system. The power circuit supplies all power required to operate the entire system, and the operator need only operate a valve to initiate a motion.

The subject invention is capable of guiding the power system in a manner (or to a position) predetermined by the control circuit. An operating position can be preselected in the control circuit and when power is admitted to the power circuit, the power element will move to the predetermined location. In this respect, the system may be likened to a hydraulic selsyn system.

It is an object of this invention to provide improved remote control of one hydraulic apparatus by another hydraulic apparatus.

It is another object of this invention to provide a hydraulic control system in which there is a controlled means responsive to actuation of a control means having a follow-up valve, and means for adjusting the phase re lationship of the controlled and control means, and in which there is no mechanical connection between the con trolled means and the control means or follow-up valve.

It is a further object of this invention to provide an improved hydraulic control system for controlling movement of a remotely located element only in response to a positive signal from a control element.

Another object of this invention is the provision of a remote control system for hydraulic appliances whereby the remotely controlled element will resist change of position from any influence other than a signal of the controlling element.

Still another object of the invention is the provision of such new and useful system which provides for and maintains motion of the remotely controlled element in direct proportion to the motion of the controlling element.

Another object of this invention is to maintain the correct relative motion (or position relationship) between I the remotely controlled element and the controlling ele'= ment of a hydraulically controlled system.

Another object of this invention is the provision of a new and useful hydraulic control system which provides automatic adjustment (or corrective positioning) of the remotely controlled and controlling elements in the event that the two should become out of correct or phase elation.

Another object of this invention is the provision of a hydraulic control system in which a predetermined position of the control element will be matched or found by a remote element.

Still another object of the invention is to provide an improved hydraulic control system in which a hydraulic circuit is used to provide a follow-up function.

A more specific object of the invention is the provision of a remotely controlled element in a hydraulic control system which has both power and control portions integral in the same housing or connected together so that their motions are coincident and are equal or proportionate.

Other specific objects are to provide a hydraulic con? trol system wherein: the power for operating both the working or remotely controlled element and the controlling element are taken from and maintained from the same source; the remotely controlled element is the one to which power is first applied; a portion of the remotely controlled element also serves as an element of the control circuit; the control circuit senses and responds to motion originating in the remotely controlled element; fluid from a power circuit is connected into the controlling element and serves as a damper, a vent and to power the controlling element; hydraulic communication between controlling and controlled circuits makes possible the operation of the entire system by a conventional valve; there is provided an adjustment valve incorporated in the controlling element which compensates for maladjustment of the remotely controlled and controlling elements, or out of phase relationship thereof; there is provided a controlling circuit which can be utilized with either a single acting or double acting working circuit; and there is provided a mechanical and hydraulic means for sensing the position of the controlled member and responding thereto.

Other specific objects of the invention reside in the structural details of the control circuit and its cooperation with the operator control; the structure for adjusting or compensating for out-of-phase relationship between the controlling and controlled elements; the structure of the new and useful controlled element or cylinder having a second cylinder therein or secured thereto and in the cooperation of these with the system.

Other and further objects of the invention are those inherent and apparent in the system as described, pictured and claimed and will become evident as the description proceeds.

To the accomplishment of the foregoing and related ends, this invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.

This invention will be described with reference to the drawings and in which corresponding numerals refer to the same parts and in which:

FIGURE 1 is a schematic view of the preferred modification of the instant system;

FIGURE 2 is a view similar to FIGURE 1 but showing a second modification thereof;

FIGURE 3 is a similar view of a third modification thereof;

FIGURE 4 is a similar view of another modification thereof;

FIGURE 5 is a similar view of yet another modification thereof;

FIGURE 6 is a sectional view of a rotary control valve utilized as a part of the system invention;

FIGURES 7A, B and C are fragmentary sectional views of the taper valve or compensating valve of this invention in three operating positions;

FIGURES 8A, B and C are similar views of a modified form of this valve;

FIGURES 9A, B and C are similar views of another modified form of this valve; and

FIGURE 10 is a sectional view through a power cylinder or remotely controlled element of the instant invention.

Reference is now made to the drawings and particularly to FIGURE 1. In this figure, the system is shown as comprising a power steering system such as for an automobile, and operation of the system is initiated by turring of a steering wheel. However, the system is adaptable to other uses as will be subsequently seen and may be initiated by other appropriate valve control. In FIGURE 1 there is shown a steering wheel 16 connected by shaft 11 to valve 12. Valve 12 is provided with a pressure line 13 joined to a pump 14A connected to reservoir 14B and is also provided with an exhaust line 15 similarly joined. Lines 13 and 15 are connected by operation of the valve 12 selectively to lines 17 and 18.

Line 17 is connected at one end to a working cylinder assembly or remotely controlled element 19. The connection is made at the piston rod end. Line 18 is also connected at one end, the butt end, to assembly 19.

Cylinder assembly 19 is also connected at part 2GP (at cylinder 25 as later explained) through line 20 to the piston rod end of first control cylinder 21 which is connected at its butt end to line 22 which receives pressure from the pump 14A at the same time as does line 13. The cylinder assembly 19 includes a piston rod 23 provided with a piston 24, the piston being apertured to receive a cylinder member 25. (Members 23, 25 may be considered as an inner ram of assembly 19.) Piston rod 23 is hollow and reciprocates on the smaller or reduced cylinder 25. Members 23 and 25 form an inner ram or second control cylinder as later explained. Thus cylinder assembly 19 comprises a double cylinder, one portion of substantially larger diameter, and one of substantially smaller diameter. One portion, the enlarged outer cylinder, is double acting which is to say it may be forced by hydraulic pressure to move in either direction and one portion, the smaller inner cylinder, is single acting.

The piston rod 26 of cylinder 21 is provided with a rack 27 for engaging a pinion 28 secured to shaft 29 of valve 12.

In this instance, control of the system is actuated by a valve 12 of the type shown in my co-pending application Serial No. 526,744, filed August 5, 1955, now Patent No. 2,854,955. It is explained in detail in that application, but forms no part of this invention per se and will be described only briefly herein for clarification. A more complete explanation may be found in the foregoing co-pending application. Other control valves may be substituted in place of valve 12 as long as fluid under pressure is selectively transferred at the initiation of the operator from line 13 to either lines 17 or 18, the transferral causes follow-up action on the piston rod 26 tending to close the valve and lines 17 or 18 are correspondingly connected to discharge line 15. For the best results, however, a valve in which pressure lines and discharge lines are communicating The valve 12, shown best in FIGURE 6, comprises an appropriate housing 30 and is known as a rotary valve. Rotary motion on shaft 11 will through lost motion connections provided by slots 31 and 32 produce corresponding rotary motion in shaft 29. During the lost motion the spool 33 is translated leftwardly or rightwardly with reference to FIGURE 6 for porting of the valve for transferring fluid under pressure to either of lines 17 or 18.

The shaft 11 is provided with pin 34 rotatable and/or slidable in helical slots 31 (only one of which is shown). Slots 31 are oppositely directed, as is explained in my co-pending application Serial No. 526,744, now Patent No. 2,854,955. Shaft 29 is provided with pin 35 rotatable and/or slidable in corresponding arcuate slots 32. A pair of prongs or teeth 36 are disposed on sleeve 40 and engage corresponding recesses or grooves 41 in spool 33. Through the combined action of pin 34, sliding in helical slots 31, prongs 36 sliding in grooves 41 and pin 35 sliding in slots 32, a rotation of shaft 11 will cause the valve spool 33 to move axially leftwardly or rightwardly with reference to FIGURE 6.

When the spool is moved rightwardly with reference to FIGURE 6, fluid under pressure is admitted through port 13A from line 13 and discharged through port 18A to line 18. Fluid is returned through line 17 to port 17A and discharged through port 15A to line 15. When the spool is moved leftwardly with reference to FIGURE 6, the lines 17 and 18 are oppositely connected to pressure line 13 and discharge line 15.

The first control cylinder, generally designated 21, consists of a conventional barrel and end cap, contains the piston rod 26 and the piston assembly generally designated 42 as best shown in FIGURES 7A-C. The gear rack 27 is integral with the rod 26 and serves to connect cylinder 21 to valve 12, as well as translate linear motion of its piston into rotary motion of the valve shaft 29.

Piston assembly 42 acts as a regular reciprocating piston during its travels in the cylinder 21, leftwardly and rightwardly with reference to FIGURES 7A-C, and as a compensating valve at each end of its stroke. The piston assembly 42 comprises an inner tapered member of frustoconical member 43 securely positioned on the rod 26 and adapted to seat in the conical seat of an outer taper or annual member 44. The seat 45 of the member 44 is tapered in a direction to cooperate with the taper of the outer surface 46 of member 43. There is thus provided an outer member 44 having an interior annular surface or interior seat 45 of annular configuration leftwardly declined with reference to FIGURES 7A-C and an inner frusto-conical member 43, fixedly secured to rod 26 and having an outer surface 46 tapered to cooperate with seat 45. Members 45 and 46 form a taper valve.

In operative neutral position, the tapers 45 and 46 assume the position of FIGURE 7B and thus form a solid piston equivalent when the taper valve is closed. The member 43 is held in closed position, as shown in FIGURE 78, by the bias of spring 47 on rod 26 engaging the ring 48 suitably secured to the end of shaft 26. A suitable O-ring seal, not shown, is provided for member 44 so that when the taper valve is closed, it is sealed externally to the barrel of cylinder 21 by such O-ring seal, and is sealed internally by the mating of the two tapered surfaces. When the taper valve is opened, in either of the positions of FIGURE 7A or 7C, communication is established between the two sides to the other. This provides a self adjusting feature of the piston and control cylinder. The cylinder 21 has a cap 49 at the bottom end and the snap ring 50 secured at its top or piston end in a recess therein.

In operation, if the piston has reached the bottom of the stroke (fully retracted) as in FIGURE 7A, the end of the piston rod 26 will bottom on cap 49, and will thus be prevented along with taper 43 from moving further (leftwardly) with reference to FIGURE 7A. If there is a pressure differential across the piston, pressure acts on the exposed rim of the outer taper 44 moving it further along the cylinder barrel 21 to the position of FIGURE 7A and opening the taper valve 43, 44. When the taper valve opens, fluid flows through the piston between the mating surfaces, now spaced, until the pressure diiferential ceases. In the position of FIGURE 7A, it will flow from the rod end of the piston to the butt end of the piston or leftwardly with reference to that figure. When the pressure differential has disappeared, the taper valve assumes the position of FIGURE 713.

Similar actuation occurs when the taper valve has reached the outer end of the cylinder. When the piston reaches the top of the stroke (fully extended) the outer taper 44 is stopped by the snap ring 50 and prevented from further travel. If a pressure differential develops across the piston, the pressure acts on the exposed end of rod 26 and of inner taper 43 and will move these parts further up the barrel to the position of FIGURE 70, thereby opening the valve, allowing oil to flow through the piston until the pressure differential ceases. The oil will flow from a leftward to rightward direction with reference to FIGURE 7C.

Tapers 43, 44 canalso be separated manually when the piston is at the top of the stroke or in the position of FIGURE 70. After the outer taper 44 stops against the snap ring 56 continued pull on the piston rod 26 will separate the tapers.- This continued pull would preferably come from rotation of pinion gear 28 by valve shafts 29 and 11 by the operator turning on steering wheel lit and through their lost motion connection which would act to extend rack 27. The form of assembly 42 shown in FIGURES 7AC is the preferred embodiment.

The preferred embodiment of the power unit and its correlative control unit is shown in FIGURE 1 as cylinder assembly 19. It is shown as a cylinder within a cylinder. The outer cylinder exerts force in both directions by hydraulic power and is known as a double acting cylinder comprised of barrel 51, end caps 49 and 53, piston 24, and piston rod 23. The inner cylinder is a single acting cylinder comprised of end cap 53, movable outer barrel 23 (which is also the piston rod 23) and stationary cylinder pipe 25. Lines 17 and 18 serve the double acting outer cylinder; line 20 serves the single acting inner cylinder.

The outer cylinder is the power cylinder of the system. It is connected into the power or pump circuit of the system. Fluid entering through line 18 to act on the exposed side of piston 24 moves the piston up the barrel or leftwardly with reference to FIGURE 1, thus extending piston rod 23. During this action, fluid is discharging through line 17. When fluid under pressure enters through line 17, the piston rod 23 will be retracted and fluid will discharge through line 18.

The inner cylinder is the second control cylinder associated with (and positively linked to) the outer or power cylinder. Its outer barrel 23 is the same piece as piston rod 23 although its operating portion of this piece is the inside volume whereas the outside surface is the portion of importance to the power cylinder. As the piston rod 23 extends or contracts, the inner volume in barrel 2?: and cylinder 25 expands or contracts.

The inner cylinder is connected through line 20 to the cylinder 21 which serves as a first control cylinder connected to the valve 12. As the column expands or contracts within ram 23, 25, hydraulic fluid flows in or out of it and must flow to cylinder 21 since the two are connected by closed hydraulic line 20. This flow will cause a related motion between inner ram 23, 25 and control cylinder 21 A suitable seal is provided between cylinder 25 and barrel 23 which preserves the separation of the inner and outer cylinders.

in operation, hydraulic fluid, oil, is stored in reservoir 6 14B and fed by pump 14A through line 13 to rotary valve 12 and at the same time through line 22 to cylinder 21. When actuation of cylinder 19 is desired wheel 19 is turned in the appropriate direction, rotating shaft 11 of the valve 12, and through the lost motion connection opening the valve to direct fluid to a line 17 or 18 and thence to the power cylinder for moving the control element 3.

If the desired turn requires the extension of the power cylinder 19 (by the operator turning the wheel to his right in FTGURE 1), pressure fluid enters the cylinder through line 13. As the fluid fills the cylinder 19, the piston rod 23 extends, the fluid from the other side of the piston 24 is discharged through line 17 through valve 12 and line 15 back to the reservoir 14B. As the rod 23 extends, the volume in ram 23, 25 is increased and to fill this enlarged volume, oil flows through line 29 from the rod end of the control cylinder 21. This transfer of fluid is powered by the pressure fluid through line 22 admitted to the butt end of cylinder 21. A partial pressure or slight vacuum induced in ram 23, 25 by the enlargement of its volume also assists this fluid transfer.

Since the cylinder 21 is joined to valve 12 by a gear train including rack 27 and pinion 28, the extension of rack 27 imparts a rotation to pinion 28 which rotation is in the same direction as the original turning of the steering wheel 19. However, because of the pin and slotted hole connections existing between shafts 11 and 29 (the lost motion connection earlier referred to) the rotation of the pinion 28 lags the rotation of the wheel Ed by a few degrees. This lag is enough to permit the valve 12 to be opened to initiate the action of the system. As long as the rotation of the wheel 19 is continued, the lag will remain {i.e., the pinion 28 will follow the wheel lit by a few degrees of lag initially established), the valve 12 will remain open and the action will continue.

When rotation of wheel 16 is stopped, the system action and pinion rotation continues for the short period of time, equal to lag time, required for the rack 27 to rotate pinion 23 the amount of lost motion and neutralize the 1 valve 12. With the valve 12 in neutral the system is stationary and fluid merely flows from line 13 across valve 12 and through line 15 back to the reservoir.

When a turn in the opposite direction is made, which requires retraction of the power cylinder, the valve and cylinder actions are similar to but the reverse of the action described above. In this instance pressure fluid enters the cylinder 1? through line 17 and as fluid fills the cylinder from the piston rod side, the rod 23 contracts and the fluid from the other side of the piston 24 (butt end of the cylinder) is discharged through line 18, valve 12 and back to the reservoir 1413. As the piston rod 23 contracts, the volume of 23, 25 is reduced and fluid is forced through line 2% into cylinder 21. Pump pressure in the butt end of the cylinder 21 (via line 22) tends to resist the retraction of the piston of cylinder 21 and thereby acts as a damper. The pump pressure against piston assembly 42 is not enough to stop retraction, since the area of piston 24 is much greater than that of pipe 25. The contraction of rack 27 then actuates valve 12 in reverse of the action described above.

The volumes of ram 23, 25, and 21 (on the rod end) are equal (when piston rods 26 and 23 are fully retracted) and the success of this systems action is believed to depend on this. Moreover, it is believed that the motions of the two cylinders must be in phase and their positions must be in proper relationship or proportion, e.g. when one is at midstroke, the other is at midstroke, etc. The taper valve 43, 44 in cylinder 21 plus the access to pump pressure fluid through line 22 assists in maintaining this relationship. Note that connection of ram 23, 25 to the butt end of cylinder 21 is also practical and workable. Thus, whichever end of cylinder 21 is chosen as the cooperating end with cylinder 23, 25 should have its volume arranged to be equal to that of cylinder 23, 25, as stated.

The taper valve operates as previously described to compensate for out-of-phase relationship. When there is too much fluid in the closed circuit consisting of cylinder 23, 25, line and the rod end of cylinder 21 (i.e. the two cylinders are out-of-phase), and the system is moving to retract cylinder 21, when rod 26 bottoms against the butt end of cylinder 21, the rod travel will stop. However, the retraction of cylinder 23, continues, and pressure in the closed circuit overcomes the spring 47 and pump pressure against the taper 44 and opens the taper valve 43, 44 by moving the outer taper 44. Fluid moves through the taper valve until cylinder 23, 25 is completely retracted, at which time flow stops, taper 43 closes and the two cylinders are again in phase. Pump pressure is overcome (even though the same pump pressure is applied against power cylinder piston 24 as against control cylinder piston 42) because the area of piston 24 is considerably larger than the area of cylinder 23, 25. Thus the force developed by pressure against piston 24 can produce a higher-than-pump pressure within the closed circuit.

If there is too little oil in the closed circuit and the system is moving to extend cylinders 23, 25, and 21, as cylinder 23, 25 extends, it will drain away the oil in the rod side of cylinder 21; pressure fluid from line 22 will tend to accelerate the extension of cylinder 21, tending to close valve 12. This means that the operator must turn wheel 10 faster than would be the case in a properly balanced system in order to keep valve 12 open so that cylinder 23, 25 can continue its extension.

This accelerated operation of valve 12 brings cylinder 21 to the end of its stroke before cylinder 23, 25 is fully extended. As cylinder 23, 25 continues to extend without a corresponding movement of cylinder 21, it will include a partial pressure in the closed system. Since pump pres sure exists on the butt-end side of piston 42, a pressure difierential is created across piston 42. The pressure diflerenetial existing across the piston of cylinder 21 forces taper 43 open, and fluid will flow through the piston from line 22 to line 2% and cylinder 23, 25. When the closed circuit is filled, as piston 24 bottoms on the rod end of cylinder 19, the difierential will disappear and the taper valve will close.

Since the areas on the two sides of the piston of cylinder 21 are not equal (the rod side is smaller by the area of the rod) and the areas on the two ends of each tapered piece differ when the tapers are closed, it ha been found preferable in addition to providing compensation by pressure alone to provide manual compensation. Thus, at the end of a stroke of rod 26 as at FIGURE 7C the operator can continue the turn of the wheel 16 in the direction being used so that taper 44 will bottom against ring 50 and the pull of the rod 26 on taper 43 will open the valve, allowing the above compensating action.

In the modified form of taper valve shown in FIG- URES SA-C, there is provided a three element taper valve, in contrast to the two element valve of FIGURES 7A-C. The tapered element 60 corresponds to the element 44, but is of lesser taper; smaller in radial extension. Element 61 corresponds to element 43 but has two tapered surfaces and cooperates with the tapered element 62, secured to the shaft 26A. In addition to the ring 48 and spring 47, which engages element 60, a second ring 48A and spring 47A, identical but oppositely disposed on shaft 26A, engage tapered element 61. Element 60 provides an outer cylindrical surface sealed to the barrel 21 (as does element 44) and has a tapered inner annular seat. Element 61 has a tapered outer surface cooperating with the inner annular tapered seat of element 60 and a second tapered inner surface cooperating with the tapered outer annular surface of element 62. The elements are movable relative one another as illustrated in FIGURES 8A-C. In addition, there is provided at the rod end of barrel 21 a projecting boss 63 against which ring 48A will bottom.

Thus, when the rod 26A is fully retracted as shown in FIGURE 8A and bottoms on cap 49 an excess of pressure in the closed circuit will force taper 60 to the position shown in FIGURE 8A and fluid will flow through the taper valve. The taper valve in neutral or operative position is shown in FIGURE 8B in which all tapered surfaces are maintained in neutral or closed position by springs 47 and 47A to form a solid piston. When the rod 26A is fully extended, as shown in the position of FIGURE and there is a deficiency of pressure in the closed circuit, pressure at the butt end of the cylinder 21 will force elements 62 and 61 to the position shown allowing the pressure on both sides of the taper valve to equalize.

In FIGURES 9A-C, there is shown another modified form of taper valve which comprises the valve of FIG- URES 8AC but including two snap rings similar to ring 56, viz. rings 59A and 59B secured in the barrel 21, one adjacent the rod end of the barrel and the other adjacent the butt end of the barrel. The boss 63 is not provided adjacent the rod end of the barrel in this instance. In operation, this taper valve allows cylinder compensation by pressure as explained for the valve of FIGURES 8A-C. However, in addition, the provision of snap rings 50A and 50B allows manual compensation by the operator. Thus, at the end of a stroke, when the rod 26A is fully extended, the operator, by further turn of wheel 10, may further extend rod 26A and force the valve to the position of FIGURE 9C, whereupon fluid will flow through the taper valve for compensation of the system. Likewise, when the rod is in the fully retracted position, the operator may further retract the rod as shown in FIGURE 9A, whereby the elements will be separated as shown for compensation of the system. It will be noted that, in this instance, fully retracted position will occur Where the element 60 engages ring 50B and further retraction will force the elements to the position of FIG- URE 9A. In this instance a space is provided between the end of the rod 26A and the barrel cap 49.

Modified forms of the system are shown in FIGURES 2 through 5. In FIGURE 2, the line 13B similar to the line 13 is connected to the valve 12 but not to the cylinder 21. The line 183 from the butt end of the cylinder 19, instead of being connected to the valve alone is also connected through 223 to the butt end of the cylinder 21.

In addition to providing a remote control steering system with pressure compensation or phase adjustment means, this system will also function to direct the power cylinder to a position predetermined by the control cylinder. Thus, it will operate as an hydraulic selsyn system. To function in this manner, the volume of the closed line 20 between the two control cylinders should be large in comparison to the volume of the control cylinder 21 for, in functioning as a prcselecting system, there is a reduction in pressure in the closed line 20 and this must be sufliciently small so that the seal between the piston of the control cylinder 21 and barrel, as well as the seal between parts 23 and 25, is not violated or broken with the result of admission of either air or pressure. In short, the system must remain tight with no change in oil volume and no admission of air in order for the position seeking function of this system to work.

With the system ofi, there is provided a preselecting function in a direction away from the closed hydraulic line 29. When the piston of the control cylinder 21 is moved in that direction by wheel 10, it creates a partial pressure in the closed hydraulic line connecting the two control cylinders. The volume of the closed line must be great enough so that the partial pressure remains below an amount capable of causing the piston seals to leak. When-power is admitted to the system through the valve .12 the partial pressure will cause the power cylinder to move in adirection to eliminate it, viz. to retract until the point of balanced pressure within the control system is reached. For best operation, the volumes should be selected to give the maximum pressure drop the seals will stand while achieving amount of preselecting desired.

In FIGURE 3, there is shown a modified form of system in which the double cylinder assembly 19 is replaced by a single power cylinder 19A and a control cylinder 25A integrally secured thereto and for operation therewith. The line Ed is connected to the butt end of the control cylinder, as in the modification of FIGURE 1, which control cylinder is provided with an extending piston rod 253 which is joined by a link 25C to rod 233 of power cylinder 19A for fixed movement therewith. Power cylinder 19A is a double acting cylinder and lines 17 and 13 are joined thereto. The two housings for cylinders 19A and 25A are connected as are the rods so that the rods 23B and 25B move simultaneously.

In operation the modification of FIGURE 3 operates identically with the modification of FIGURE 1.

In FIGURE 4 another modification is shown which is similar to the modification of FIGURE 3 except that a double acting control cylinder is provided in lieu of single acting control cylinder 25A and is connected to control cylinder 21 by lines 20 and MA. Line 2t} connects the butt end of cylinder 25D with the rod end of cylinder 21 and line 20A connects the rod end of cylinder 25D with the butt end of cylinder 21. However, it is preferred to have the control cylinder single acting as cylinder 25 or 2513.

In FIGURE 5 there is shown a further modified form of a system in which the cylinder comparable to 19 of FIGURES 1 and 2 is modified as shown to a single acting cylinder 19B. In this instance, lines 15 and 1.3 are connected to the valve 12 and line 18 is connected to the butt end of cylinder 1913 as explained before. A line 1713 is substituted for line 17 and connects the port 17A to the discharge line 15, so that when the wheel is turned in a direction which would normally connect pressure line 13 with cylinder line 17 in the modification of FIGURE 1, it connects pressure line 13 through line 1713 to discharge line 15. At the same time line 18 is connected to discharge so that the piston rod of single acting cylinder 19B is permitted to retract under outside force. When the wheel do is turned in the opposite direction, line 13 is connected to line 18 and fluid under pressure is delivered to the butt end of the cylinder 193 to extend the rod.

The cylinder assembly 19 is shown in vertical section in FIGURE 10. In that figure, the piston rod 23 which also serves as a barrel on the inner cylinder is shown cooperating with the cylinder 25 and provided with extending rod end 23C. Piston 24 is shown secured thereto and seals 76 74 (O-rings) are shown sealing respectively the cap 49 to the barrel, the piston 24 to the cylinder 25, piston rod 23 to cap 49 the piston 24 to the barrel and the cap 53 to the barrel. A wiper seal 74 is provided in cooperation with O-ring "72. At 53A is shown a suitable means for connecting cap 53 to other structure.

It will thus be seen that there is provided a new and useful hydraulic control circuit or system as described and claimed, which provides a hydraulic linkage between a control and controlling element and which has a sensing ability and provision for correcting misadjustment between remote (controlled or Working) and control apparatus or elements, a pre-selecting function and a followup function by hydraulic transfer means.

As many widely difl'ering embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the specific embodiments described are given by way of example only and the invention is limited only by the terms of the appended claims.

What is claimed is:

1. In a hydraulic system, a normally open valve having a first and second actuating means and a lost motion connection therebetween, means for supplying fluid under pressure to said valve and means for discharging fiuid therefrom, a power cylinder assembly having a piston connected to said valve for actuation thereby, a first control cylinder connected to said second actuating means, means for providing fluid under pressure to one end of said first control cylinder, said power cylinder assembly including a single acting cylinder and a closed circuit connecting said single acting cylinder to the other end of said first control cylinder, said single acting cylinder acting as a second control cylinder and connected to and movable by said power piston, said valve being so constructed and arranged that actuation of said first actuating means before actuation of said second actuating means will actuate said valve to transfer pressure to said power cylinder, and said closed circuit having a volume substantially in excess of the volume of said first control cylinder.

2. An improved hydraulically operated control system of the type having a dou'ble acting power cylinder havin a piston, a source of hydraulic fluid under pressure, lines interconnecting the power cylinder and source of hydraulic fluid under pressure, a control valve interposed in the lines, a first hydraulic control cylinder having a piston rod, a second control cylinder mechanically connected to and actuated by the piston of said double acting power cylinder, a conduit interconnecting said first and second control cylinders, and a conduit connecting the end of said first control cylinder that is not connected to said second control cylinder to the source of hydraulic pressure; the improvement comprising said control valve having two actuating means interconnected by a lost motion structure; and one of said actuating means being secured to the piston rod of said first control cylinder.

3. The structure of claim 2 further characterized by said control valve being a normally open valve.

4. In a hydraulic system, a normally open valve having a first and second actuating means and a lost motion connection therebetween, means for supplying fluid under pressure to said valve and means for discharging fluid therefrom, a double acting power cylinder having a piston rod and having one passage at its end remote from its rod end connected to said valve and another passage at its rod end connected to said valve, said valve operating in response to action of Said first actuating means selectively to transmit fluid under pressure to one of said passages and discharge fluid from the other of said passages, said second actuating means operable to conclude said transmission, a first control means secured to and actuated by said double acting power cylinder piston rod, a second control means secured to and actuating said second actuating means, and flexible control transmission means operably interconnecting said first and second control means.

5. The structure of claim 4 in which said first and second control means are hydraulic cylinders and said flexible control transmission means is a hydraulic conduit.

6. The structure of claim 5 in which said first control means is a hydraulic cylinder formed integrally with the piston rod of said double acting power cylinder.

7. The structure of claim 5 in which said second control means includes compensating means permitting transfer of fluid from one end to the other of said second control means cylinder when pressure in said flexible control hydraulic conduit varies from a predetermined one.

References Cited in the file of this patent UNITED STATES PATENTS 561,747 Worthington June 9, 1896 2,261,444 Neubert Nov. 4, 1941 2,273,408 Woodward Feb. 17, 1942 2,349,295 Napier May 23, 1944 2,589,850 Orelind et a1 Mar. 18, 1952 2,688,258 Haynes et al Sept. 7, 1954 

